1. Field of the Invention
This invention relates to earth boring bits, lubricated with a system which includes a hydrostatic pressure compensator to balance the internal pressure of the lubricant inside the bit with the hydrostatic pressure of a liquid drilling fluid that surrounds the bit during drilling. In this combination, the specific improvement relates to the seal and bearing assembly between each cutter and bearing shaft.
2. Background Information
A two piece bearing construction is disclosed in U.S. Pat. No. 4,600,064, "EARTH BORING BIT WITH BEARING SLEEVE", July 15, 1986. An internally tapered and threaded bearing sleeve is made up on a mating, externally threaded bearing lug. The mouth of the sleeve engages a shoulder on the base region of the bearing lug and has a selected radial thickness such that the sleeve may be made up to a selected torque. Also, the bearing sleeve has a length greater than that of the threaded portion to define a thick walled inner end region to receive a resilient retainer ring in a groove that provides a selected section over the threads on the interior of the sleeve.
A successful earth boring bit having an improved rigid face seal assembly is disclosed in U.S. Pat. No. 4,516,641, "EARTH BORING BIT WITH PRESSURE COMPENSATING RIGID FACE SEAL", May 14, 1985. Further improvements are disclosed in U.S. Pat. No. 4,666,001, "EARTH BORING BIT WITH IMPROVED RIGID FACE SEAL ASSEMBLY", May 19, 1987.
An improvement that utilizes a rigid face seal assembly with a two piece bearing in a rock bit is disclosed in an application entitled "EARTH BORING BIT WITH TWO PIECE BEARING AND RIGID FACE SEAL ASSEMBLY", Ser. No. 023,170 filed Mar. 9, 1987, now U.S. Pat. No. 4,753,303.